Roll stand

ABSTRACT

A stand having three rolls, one of them being a work roll is connected to a drive giving energy required for pulling the bar being rolled through the pass and for deformation of the bar. Two other idle rolls are integrated with drives for their acceleration. For this purpose the idle rolls are made hollow and installed on stationary axles. The hollow of each idle roll accomodates an electric stator winding connected to an alternating current power source, while the internal surface of the roll, opposite to the stator winding, mounts a circular insert made of an electric conductive material. An air gap is provided between the stator winding and the circular insert. All this taken together forms an electric motor in each idle roll to accelerate the idle rolls without any external drive.

United States Patent [1 1 Borisenko et al.

[ ROLL STAND [22] Filed: Sept. 16, 1974 211 Appl. No.: 506,747

[52] US. Cl. 72/249; 72/201; 72/224 [51] Int. Cl B2lb 35/00 [58] Field of Search 72/249, 224; 100/172;

[56] References Cited UNITED STATES PATENTS 1,733,379 10/1929 Lowy 198/127 E 1 Aug. 12, 1975 Primary Examiner-Milton S. Mehr Attorney, Agent, or FirmWaters, Schwartz & Nissen [5 7] ABSTRACT A stand having three rolls, one of them being a work roll is connected to a drive giving energy required for pulling the bar being rolled through the pass and for deformation of the bar. Two other idle rolls are integrated with drives for their acceleration. For this purpose the idle rolls are made hollow and installed on stationary axles. The hollow of each idle r011 accomodates an electric stator winding connected to an alternating current power source, while the internal surface of the roll, opposite to the stator winding, mounts a circular insert made of an electric conductive material. An air gap is provided between the stator winding and the circular insert. All this taken together forms an electric motor in each idle roll to accelerate the idle rolls without any external drive.

4 Claims, 5 Drawing Figures PATENTEDAIJEI 2i975 9 30 SHEET 2 ROLL STAND The present invention relates to metal rolling and more particularly to roll stands of a unit-design mill for longitudinal rolling of solid and hollow metal bars.

At present, roll stands are used having principally two or three rolls.

In two-high mill stands the rolls are installed at an angle of 45 to the horizontal plane, while each pair of rolls in the stands of a rolling mill is positioned at an angle of 90 in relation to the pair of rolls of the adjacent stand.

In three-high mill stands all three rolls are installed at an angle of 120 in relation to each other, while each stand of a rolling mill is turned around the rolling axis through a 60 angle in relation to the adjacent stand.

The rolls in a known two-high mill stand are brought into rotation from a motor through a gear reduction unit and an intermediate gearing. A pair of rolls receives rotation through a hyperbolic gearing train.

Said two-high mill stand mounted on the housing of the master reduction unit is actually of no separate importance as a work stand and should be considered together with the design of the master drive reduction unit intended for transmitting torque simultaneously to a number of similar stands assembled in a unit.

Utilization of precision gearings in combination with spiral gear rolls in the stand master drive made it possible to exclude clutches and spindles from the drive and to increase rolling speed to 60 rn/s.

Realization of the high-speed rolling process requires higher accuracy in manufacturing the gearing of the reduction unit. Therefore, the gearing of the stand master drive is manufactured according to a high degree of accuracy.

Together with certain favourable technological and design features the known two-high mill stand .inheres the following disadvantages.

Increased rolling speed in the stand has led to the need of additional measures for improving the dynamic characteristics of the stand, such as, use of vibration dampers in the master reduction unit of the drive, which made the reduction unit design still more complicated.

The design of the stand master drive reduction unit is exceptionally complicated, the reduction unit is very heavy in weight, its units are manufactured according to high grades of accuracy, causing a several-fold increase in the cost of manufacturing the separate units of the stand.

Also known is a two-high mill stand whose rolls are brought into rotation by variable-speed electric motor through a common transfer reduction unit, individual reduction units for each stand integrated with pinion stands and positioned along the frame of a line of stands, and through drive spindles with Hookes joints.

The major disadvantage of this stand is associated with the complex design of the master drive. Incorporation of the bulky equipment in the master drive of the stand substantially extends the overall dimensions of the stand unit as well as its weight.

In addition, incorporation in the master drive of spindles with Hookes joints, as experimental data have shown, leads to the generation of substantial oscillations of roll axles and correspondingly the rolls themselves cantilever-mounted on these axles. The amplitude of roll oscillations in separate cases reaches rather high values, which interferes with the allowances specitied for rolled products.

Substantial mechanical oscillations of the rolls in these stands affect not only the geometrical dimensions of rolled products, but also the durability of bearing units of the stand, reducing it markedly.

The design is known of a three-high mill stand with a single input shaft and the internal transfer of rotation by means of bevel gearing, used primarily for rolling metal bars from carbon and low-carbon steel. Minimum diameter of rolls in these stands is 250 mm, while maximum bar rolling speed in these stands is 45 m/s.

Various bevel gearing combinations are employed in the stand of this design, and the rolls can be installed either on rotating or non-rotating axles.

Disadvantages of the designs of three-high mill stand being described here include accomodation inside the stand of bevel gearing which requires high accuracy of manufacture to be able to operate at high speeds. In addition, with the internal transfer of rotation the supporting capacity of bearing units and bevel gearing is reduced as compared with two-high mill stands because in three-high mill stands the overall dimensions of bearing units and bevel gearing are limited by the corresponding ends of the adjacent rolls and their crossing axles.

There is a design of three-high mill stand with a highpower drive connected only with one roll, and two idle rolls.

This design eliminates a number of disadvantages found in three-high mill stands, but at the same time it brings forth a number of new disadvantages.

The angle of nip in the stand of this design is three times less as compared with the preceding three-high mill stands, which adversely affects the possibility for further increase of rolling speed and besides, the operating conditions for the output roll fittings are worsened.

At intervals in mill operation the idle rolls reduce their rotation speed to cause mismatching of roll rotation speed in the stand. At restarting the rolling process, additional dynamic loads occur in the stand at the moment of nipping the bar.

Apart from that, wear or rolls is more intensive in this stand.

There is a design of a three-high mill stand with a high-power drive connected only with one roll, and a special auxiliary drive for two other rolls having no mechanical connection with the drive roll or between each other. The special auxiliary drive for two rolls comprises boxes stationary installed on the housing carriers, said boxes accomodating turbine wheels installed on the roll axles. A jet of liquid is discharged at high velocity from a nozzle installed on the box housing in the direction tangential to the turbine wheel to rotate the latter (e.g. see US. Pat. No. 3,611,777, cl. 72-249, October 1971).

A disadvantage of this design of the stand is that incorporation of hydraulic drives to accelerate idle rolls, though eliminates bevel gearing, affords no possibility for a compact layout of the stand to minimize the overall dimensions of the stand by creating a compact builtin drive, using the existing elements of the stand construction (stand carriages, rolls).

However, the analysis of the trends in the development of high-efficiency rolling equipment has revealed the tendency of developing compact, small-size designs ensuring its maximum possible reliability in operation.

Utilization of hydraulic drives to accelerate loose rolls requires incorporation of precision hydraulic equipment which, in addition, is liable to extensive wear and needs reliable seals.

Apart from that, a disadvantage of this stand is that it includes no elements for synchronizing the rotating speed of two loose rolls with that of the drive roll, which substantially complicates functioning of the mill stand and the stand line of the rolling mill at high-speed operation.

Also known are designs of four-high mill stands which are very uncommon at the present time. Disadvantages of these stands include their complicated design and low durability.

The object of the present invention is to provide a roll stand that would permit to increase rolling speed as compared with the existing makes of stands of the similar type.

Another object of the present invention is to provide a roll mill that would be of smaller overall dimensions and weight due to a better layout of stand units.

One more object of the present invention is to provide a roll stand that would be free of impact loads and vibration.

Still another object of the present invention is to provide a roll mill which due to its simpler construction would permit to reduce the cost of its manufacture and of servicing its equipment.

These and other objects are achieved by provision of a roll mill stand of unit design for rolling metal bars, comprising a housing with carriages in which bearing units are mounted carrying an axle with a work roll and at least one axle with an idle roll, and a drive for bringing rotation to the work roll, and drives for the idle rolls. According to the invention each idle roll, to form its individual drive, is installed on the stationary axle and is of hollow construction, whereas inside its hollow on the axle an electric stator winding is accomodated which is connected to an alternating current supply source, while the internal surface of the roll opposite to the electric stator winding mounts a circular insert made of electric conductive material, and an air gap is provided between the electric stator winding and the circular insert.

It is convenient to make the circular insert in the form of a laminated ring from hard-magnetic material which would allow the manufacture of these insert to be substantially simplified and their cost be considerably reduced.

It is also convenient to make passages in the stationary axle of the idle roll to bring air into the hollow of the roll and also to make radial passages and longitudinal passages along the axis of the roll in the body of this roll to direct air from the hollow of the roll to its side surface.

The above passages for air flow would improve cooling of the electric stator winding.

It is expedient to direct the longitudinal passages in the roll opposite to the direction of roll rotation and at a certain angle to the direction of its axis that would permit a reduction in the starting power of the roll electric motor.

The invention has resulted in the development of a roll stand permitting a considerable increase in rolling speed as compared with the existing makes of stands of the similar type, that will substantially raise the rolling mill productive capacity and improve its performance characteristics, as well as make the stand more compact, reduce its overall dimensions and weight.

In order to make the present invention more readily understood an actual embodiment thereof will now be described in more detail with reference to the accompanying drawings, in which:

FIG. 1 is a plan view of a unit-design mill for rolling metal bars, incorporating the roll stand according to the invention;

FIG. 2 is a view taken along the rolling axis, partly broken, of the roll stand constructed according to the invention;

FIG. 3 is a view, partly broken and enlarged, of the unit A in FIG. 2;

FIG. 4 is a plan partly broken view of an idle roll, illustrating a horizontal air passage directed at an angle to the roll axis;

FIG. 5 is a view of the unit B taken along the arrow C in FIG. 3.

A rolling mill of unit design illustrated in FIG. 1 comprises: a common variable-speed electric drive 1, a combination reduction unit 3 of the mill, connected to the common drive through a coupling 2, a housing 4 of a roll stand line, which mounts roll stands 5, output shafts 6 of the reduction unit and electric sensors 7 to sense rotational speed of the output shafts 6 for the stands 5.

The sensors 7 are fitted on tail ends (not shown) of the outpUt shafts 6 of the reduction unit 3 at the side of the latter opposite to the location of the roll stands 5.

The roll stand 5 (FIG. 2) according to the invention comprises a housing 8 which accomodates carriages 9, 10, ll, 12 and 13 wherein a work roll 15 is installed on a drive shaft 16, and two similar idle rolls l7 and 18 are installed on stationary axles 19 and 20.

To make the description simpler only one idle roll 17 will be described further on.

The hollow idle roll 17 (FIG. 3) comprises a hollow body 21 with a stationary electric stator (stator winding) 22 installed on a stationary axle l9 inside the body.

The stator 22 is fitted on the stationary axle 19 by means of an adapted circular bush 23.

Fixed on the internal surface of the hollow body 21 of the roll is a circular insert 24 made from electric conductive (laminated hard-magnetic) material. The circular insert 24 is locked in the hollow body by a bush 25 and rotates together with the latter. The hollow body 21 is installed on antifriction bearings 28, 29 through supporting circular bushes 26 and 27.

The stationary axle 19 of the idle roll 17 has passages 30 and 31 to deliver lubricant to the bearings 28, 29 and also passages for return of lubricant (not shown). Apart from that, an external longitudinal slot (not shown) is provided on the stationary axle 19 to lay down electric wires for power supply to the stator 22.

To cool the stator 22, the stationary axle 19 has passages 32 and 33 to deliver dry compressed air, while the body 21 of the hollow roll 17 has vertical passages 34 and horizontal passages 35 to evacuate compressed air from a hollow 36 of the roll.

It should be noted that horizontal passages 35 directing compressed air to the side surface of the body 21 of the hollow roll 17 can be directed not strictly perpendicularly to this surface, but turned as illustrated in FIG. 4 in a horizontal plane in relation to the roll axis at a certain angle in a direction opposite to that of roll rotation. In this case, compressed air discharged from the passages 35 will create a reactive torque which, adding to the electromagnetic torque, will reduce the needed starting power of the electric motor of the roll. Thus, favourable conditions can be provided for opera tion of the roll motor at speeding-up of rotation and upon stopping of the roll in the course of operation.

Antifriction bearing 28, 29 are fixed on the stationary axle 19 by means of nuts 37.

To synchronize rotational speeds of the idle rolls 17 and 18 and that of the work roll the roll stand employs contactless sensors. One stationary portion of sensors 38 and 39 is matched with the end surfaces of the carriages 9 and 12, facing these rolls, while the other movable portion of these sensors is matched with the end surface of the removable circular bush 27 (FIG. 25) to face the stationary portion of sensors 38 and 39. The end surface of the removable circular bush 27 bears protrusions 40 and recesses 41.

The design and principle of operation of such contactless sensors are commonly known and well described in the relevant technical literature.

The above described design of the roll stand is compact, features high rigidity, light weight, while the rotating parts are easily liable to dynamic balancing.

The roll stand operates as follows.

A rolling mill operator at the control desk (not shown) of the mill illustrated in FIG. 1 makes preparations for switching on all electric circuits (not shown): to control the common variable-speed drive, to control an alternating current power supply with working frequency above 50 Hz and, to synchronize rotational speeds of the work and idle rolls. Here electric circuits can be applied known from the relevant technical literature and suitable for the given operating conditions.

Then, the operator actuates cooling of the stator 22 by admitting compressed air to the hollow 36.

The control and measuring apparatus (not shown) provided on the mill gives permission for engaging the variable-speed electric drive and electric power sources for feeding the stator windings only if lubricant is present in the bearings and compressed air is found in the hollow 36 of the idle rolls.

Thereafter, the rolling mill operator switches on the electric drive 1 and the stator winding power supply. The electric drive by means of the coupling 2 transmits rotation to the common reduction unit 3 which in its turn by means of the output shafts 6 and drive shafts 16 of the roll stands 5 brings rotation to the work rolls 15, whereas the electric sensors 7 fitted on the tail ends of the output shafts 6 of the reduction unit 3 are sensing rotational speeds of the work rolls 15.

Electric signals from sensors 7 are sent to the electric power supply control circuits and to the rotational speed comparison circuits for the work roll 15 and each idle roll 17 and 18.

As a result of feeding an increased frequency alternating current to the stator 22 a rotating magnetic field is created in an air gap 42 between the stator and the circular insert 24 made from electric conductive material (laminated ring from hard magnetic material), said magnetic field interacting with the circular insert installed on the internal surface of the body starts rotating the body and consequently the roll 17 as well.

The work roll 15 through the electric sensor 7 acts on the functioning of the stator winding power supply to adjust its operation and sets the rotational speed of each of the idle rolls 17 and 18 to be close to the rotational speed of the work roll 15.

To prevent lagging of the rotational speed of the idle rolls 17 and 18 behind that of the work roll 15, occurring due to aerodynamic losses caused by friction between rolls 17, 18 and water delivered to a pass 43 for cooling the latter, the power supply electric control circuit of each idle roll provides for additional synchronization of the rotational speed of the idle rolls 17 and 18 and the rotational speed of the roll 15.

For this purpose, the end surfaces of the carriages 9 and 12 mount the stationary portions of electric sensors 38 and 39 connected in the rotational speed comparison circuits for the idle rolls and the work roll 15.

In their turn, the above circuits by means of electric feedbacks are connected to the power suuply control circuits to correct power supply functioning.

The moment at which the given rolling speed is set on the work roll 15 coincides with the termination of synchronizing the rotational speed of the idle rolls l7 and that of the roll 15.

The rolling mill is ready for operation.

Further on, the process of rolling metal bars in the mill is effected in the direction indicated by arrows shown in FIG. 1.

An important advantage of the herein disclosed roll stand is utilization in it of contactlcss electric motors built in the idle rolls for their acceleration, and synchronization of their rotational speed with that of the work roll.

This structural embodiment of idle rolls permits a substantial increase in the rolling speed and consequently in the rolling mill productive capacity.

This higher rolling speed is achieved due to freeing the roll stand design of bevel gearing, whereas the angle of nip remains the same as when using bevel gearing.

Elimination of bevel gearing in the roll stand to transfer rotation to the rolls allows the diameter of the rolls to be varied for the most favourable selection, of their diameter and the reduction rate of the bar being rolled in the stand pass for maximum processing benefit.

This structural embodiment of the idle rolls also allows the overall dimensions and the weight of the roll stand to be considerably reduced and the rigidit and strength of the stand be improved.

Simple design of the combination reduction unit incorporating spur gearing used in the roll stand of the instant invention also helps to achieve higher rolling speed in the stand.

The roll stand as described herein opens way for making up rolling equipment possessing high dynamic characteristics and for a wide range of rolling speed adjusting beginning with a rolling speed specific for roughing stand and concluding with a rolling speed specific for finishing stands of wire mills.

The invented roll stand is able to reach rolling speed of m/s and higher, not known yet in the art.

The given roll stand is much superior over the hydraulic arrangement for rotating idle rolls, because it frees the rolling mill of precision hydraulic equipment and regulators whose operation on the mill entails much trouble and difficulty. Besides that, use of highpressure hydraulics causes considerable difficulties when creating a system of roll speed adjustment so as in rolls speed synchronization.

One of the advantages featured by the new roll stand is that electrical engineering elements employed therein (stator 22 and circular insert 24 of hardmagnetic material, FIG. 3) are replaceable parts of the stand and can be used repeatedly, actually an unlimited number of times. Durability of said electrical engineering elements is increased not only due to favourable operating conditions, but also because of possibly having synthetic coating. Thus, the stator 22 can be coated with epoxy resin to improve its mechanical strength and protect against penetration of oil and moisture into the winding.

This roll stand of unit-design mill combines simplicity and small size with most wide processing capabilities as compared with any other roll stands of unit design.

We claim:

1. A roll stand of unit-design mill for rolling metal bars, comprising: three rolls including one work roll and two similar idle rolls; a drive shaft for rotating said work roll and for transmitting energy required for deformation of the bar being rolled; said idle rolls being each installed on a stationary axle, said axle being made hollow and having an electric stator winding positioned thereon in the hollow of said roll and being connected to an alternating current power supply, a circular insert of an electrically conductive material being installed on the internal surface of said roll opposite to said stator winding, an air gap being provided between said stator winding and circular insert, thereby forming an electric motor in each said idle roll for accelerating the latter.

2. A roll stand as set forth in claim 1, wherein said circular insert is made in the form of a laminated ring from hard-magnetic material.

3. A roll stand as set forth in claim 1, wherein said stationary axle of the idle roll has passages for air delivery into the hollow of said idle roll for cooling said stator winding, while the body of said roll has radial passages and longitudinal passages along the axis thereof to draw air from the hollow of said roll to an aside surface thereof.

4. A roll stand as set forth in claim 3, wherein the longitudinal passages of said idle roll are directed at a angle to the direction of its axis, opposite to the sense of rotation of said roll. 

1. A roll stand of unit-design mill for rolling metal bars, comprising: three rolls including one work roll and two similar idle rolls; a drive shaft for rotating said work roll and for transmitting energy required for deformation of the bar being rolled; said idle rolls being each installed on a stationary axle, said axle being made hollow and having an electric stator winding positioned thereon in the hollow of said roll and being connected to an alternating current power supply, a circular insert of an electrically conductive material being installed on the internal surface of said roll opposite to said stator winding, an air gap being provided between said stator winding and circular insert, thereby forming an electric motor in each said idle roll for accelerating the latter.
 2. A roll stand as set forth in claim 1, wherein said circular insert is made in the form of a laminated ring from hard-magnetic material.
 3. A roll Stand as set forth in claim 1, wherein said stationary axle of the idle roll has passages for air delivery into the hollow of said idle roll for cooling said stator winding, while the body of said roll has radial passages and longitudinal passages along the axis thereof to draw air from the hollow of said roll to an aside surface thereof.
 4. A roll stand as set forth in claim 3, wherein the longitudinal passages of said idle roll are directed at a angle to the direction of its axis, opposite to the sense of rotation of said roll. 